Both shots end on the same framing. The top camera never moved: it zoomed from 35 to 70 mm. The bottom one rolled from 6 m to 3 m on a 35 mm lens. In a zoom, everything grows together, like a crop. In a dolly, near things grow faster and slide past far ones. That's parallax, and only a moving camera makes it.

In 2025, the team behind CameraBench labelled 3,381 video clips move by move. They write that beginners can mix up a zoom and a dolly, and that training fixes it; their experts were more than 15 percent more accurate.

Try the test: crop a zoom's first frame and it matches the last one. A dolly's never lines up. Do both at once, in opposite directions, and you get Hitchcock's dolly zoom.

The hall, the stand-ins and the lens are our own, built and lit in code.

Which one did you pick, before the answer?

Sources: Lin et al., Towards Understanding Camera Motions in Any Video (CameraBench), NeurIPS Datasets and Benchmarks Track (2025).
Music: made with ElevenLabs Music. Sounds: made by us; zoom servo from Apple's iLife effects.